1. Field of the Invention
The present invention relates to an ultrasonic flowmeter and a manufacturing method thereof. This application is based on Japanese Patent Application No. Hei 11-212940, and the contents of which are incorporated herein by reference.
2. Description of the Related Art
Recently, ultrasonic flowmeters have been used to measure the flow rates of fluids.
Each of these ultrasonic flowmeters has two piezoelectric transducers which are separated by a predetermined distance along the longitudinal direction of the pipe in which the fluid flows. In this ultrasonic flowmeter, ultrasonic waves are reciprocally transmitted between these two piezoelectric transducers and the flow velocity of the fluid in the pipe is measured by the difference between the transmission times of the reciprocal transmissions, and the flow rate is determined from the flow velocity.
In this ultrasonic flowmeter, the piezoelectric transducers are ring shaped and are fixed to the pipe, which is inserted through the piezoelectric transducers, by adhesives. However, in this structure, spaces are formed between the inner surfaces of the piezoelectric transducers and the outer surface of the pipe by bubbles in the adhesives and the like. Therefore, the transmission of ultrasonic waves between the piezoelectric transducers and the fluid flow in the pipe is insufficient, and problems may arise in that the flow rate cannot be exactly measured.
Furthermore, the piezoelectric transducers can be fixed to rings which are already fixed to the pipe. However, in this case, spaces can also be formed between the rings and pipe, similarly to the above-described case, and this can also give rise to problems in the measurement of the flow rate.
The present invention is provided in view of the above-described situation, and the purpose of the present invention is to provide an ultrasonic flowmeter which can measure the flow rate exactly and a manufacturing method thereof.
The present invention, to achieve the above objective, provides an ultrasonic flowmeter having a pipe through which a fluid to be measured flows, and measurement portions separated on the pipe by a predetermined distance along the longitudinal direction of the pipe; and which determines a flow rate of the fluid from a flow velocity which is determined from a difference in transmission times for reciprocal transmissions of ultrasonic waves between the measurement portions; and is characterized in that the measurement portions each comprise a transducer fixing member having an arc shaped indentation into which a part of the pipe can be fitted, and a piezoelectric transducer fixed to the transducer fixing member; and the pipe and the arc shaped indentation are closely fixed to each other by an adhesive.
The present invention also provides an ultrasonic flowmeter having a pipe through which a fluid to be measured flows, and measurement portions separated on the pipe by a predetermined distance along the longitudinal direction of the pipe; and which determines a flow rate of the fluid from a flow velocity which is determined from a difference in transmission times for reciprocal transmissions of ultrasonic waves between the measurement portions; and is characterized in that the measurement portions each comprise a piezoelectric transducer closely fixed by an adhesive to a part of the pipe, so as to have an arc shape along the circumference of the pipe.
The present invention also provides an ultrasonic flowmeter having a pipe through which a fluid to be measured flows, and measurement portions separated on the pipe by a predetermined distance along the longitudinal direction of the pipe; and which determines a flow rate of the fluid from a flow velocity which is determined from a difference in transmission times for reciprocal transmissions of ultrasonic waves between the measurement portions; and is characterized in that the measurement portions each comprise a piezoelectric transducer closely fixed on a part of the pipe so as to have an arc shape along a circumference of the pipe, and a tube covering an outer surface of the pipe at a position of the piezoelectric transducer is provided and closely fixing the piezoelectric transducer to the pipe by pressing the piezoelectric transducer against the pipe.
The present invention also provides a manufacturing method of an ultrasonic flowmeter having a pipe through which a fluid to be measured flows, and having measurement portions separated on the pipe by a predetermined distance along the longitudinal direction of the pipe; and which determines a flow rate of the fluid from a flow velocity which is determined from a difference in transmission times for reciprocal transmissions of ultrasonic wave between the measurement portions; and is characterized in that the measurement portions each comprise a transducer fixing member having an arc shaped indentation into which a part of the pipe can be fitted, and a piezoelectric transducer fixed to the transducer fixing member; and having a step of closely fixing the transducer fixing member to the pipe by an adhesive by fitting and pressing the pipe on the arc shaped indentation via the adhesive.
The present invention also provides a manufacturing method of an ultrasonic flowmeter having a pipe through which a fluid to be measured flows, and having measurement portions separated on the pipe by a predetermined distance along the longitudinal direction of the pipe; and which determines a flow rate of the fluid from a flow velocity which is determined from a difference in transmission times for reciprocal transmissions of ultrasonic waves between the measurement portions; and is characterized in having steps of providing piezoelectric transducers which compose the measurement portions on an outer surface of the pipe along the circumference of the pipe via adhesives, and closely fixing the pipe by adhesives by fitting and pressing the pipe on arc shaped indentations which are formed on transducer fixing members via the piezoelectric transducers.
The present invention also provides a manufacturing method of an ultrasonic flowmeter having a pipe through which a fluid to be measured flows, and having measurement portions separated on the pipe by a predetermined distance along the longitudinal direction of the pipe; and which determines a flow rate of the fluid from a flow velocity which is determined from a difference in transmission times for reciprocal transmissions of ultrasonic waves between the measurement portions; and is characterized in having steps of providing piezoelectric transducers which compose the measurement portions on an outer surface of the pipe along the circumference of the pipe, providing covering tubes on an outer surface of the pipe at positions of the piezoelectric transducers, and closely fixing the piezoelectric transducers to the pipe by pressing the piezoelectric transducers against the outer surface of the pipe along the circumference of the pipe using the tubes.